Lesson 12: Sensory System: Thalamus Flashcards Preview

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Flashcards in Lesson 12: Sensory System: Thalamus Deck (40):

How does sensory-motor integration work?

This process has important clinical implications. When your client is receiving stimuli, including therapeutic input, it is constantly being modified against a background of other stimuli, compared with prior experience, and modified according to the quality of information from the entire environment.


Where does sensory-sensory, and sensory-motor integration happen?

The lateral spinothalamic pathway, carrying pain information, is a useful example to identify many sensory integration centres. The primary neuron brings in the pain signal.
There is plenty of evidence that repeated input of pain stimuli physically modifies the membrane receptors in the secondary neuron.


In sensory-sensory and sensory-motor integration, what is an option for a signal?
Where does the signal go after that?

- One signal may go to a reflex withdrawal.
- The signal may cross the spinal cord and ascend in the lateral spinothalamic pathway, giving off information to a network of nuclei, the reticular system
- The signal continues to the thalamus


Which is the most important sensory-motor integration centre?
What structures are receiving stimuli?
Where can the information go? (5)

- The thalamus is probably the most important sensory-motor integration centre.
- There are sensory nuclei (VPM and VPL for example) receiving information, integrating it within the thalamus.
It may inform the cerebral cortex (conscious level), it may inform the basal ganglia (modifies motor programs) or it may inform other sensory centres within the thalamus. It may also send information to the pain modulation centres in the brainstem, or descend to the dorsal horn


Once signals reach the cerebral cortex, how is it triaged?

In cerebral cortex, it is again met by modifying input of all types, information as to how “important” the pain is and the emotional palate upon which it is “experienced”.


In chronic pain, how does the circuitry work?

In the treatment of chronic pain, the original signal source may have “healed”, but the new circuit has been required to respond to the memory of the pain and becomes a very different process to treat chronic pain, a real and persistent circuit.


Why is the diencephalon considered a "primitive" brain?

Many sources of sensory input never reach the conscious level


What does the diencephalon develop from? Where is it located?

Develops from the forebrain and is located on either side of the third ventricle, surrounded by the telencephalon (cerebral, basal ganglia and white matter in between).


What is the function of the hypothalamus?

The hypothalamus is responsible for the internal regulation of hormones and the vital body processes such as temperature regulation, thirst, growth, sexual function etc.
- Part of the ANS - maintain homeostasis


Where does the hypothalamus have input to?

It has input to the pituitary gland and important circuits to the cranial nerve nuclei to participate in many of the processes governed by the limbic system


What is the function of the epithalamus?

It is known to regulate sleep cycles; secretes melatonin in response to the day-night cycle, regulates diurnal rhythms of the brain


What are the functions of the VPLM and VPL of the thalamus?

The VPM and VPL were relay stations in the sensory pathways from the head and neck and the body respectively.


What are the functions of the lateral and medial geniculate bodies of the thalamus?

The lateral geniculate body and medial geniculate body, clustered with the thalamus are primary nuclei for vision and hearing respectively


What are the functions of the ventral anterior and lateral nuclei of the thalamus?

The ventral anterior (VA) and ventral lateral (VL) nuclei are involved with motor control.


What is the function of the dorsomedial nucleus?

Where is it located and where does it project, terminate?

Is involved with the many functions of the frontal lobe.

Next to the 3rd ventricle and projects forward to the anterior limb of the internal capsule, between the thalamus and the caudate nucleus. Fibres from here leave the thalamus and travel in the anterior limb of the internal capsule to their destination in the frontal lobe.


What can lesions of the thalamus cause?

- Can produce some language impairment (i.e., subcortical/thalamic aphasia)
- Thalamic syndrome


What are the 4 parts of the diencephalon?

Thalamus, epithalamus, subthalamus, hypothalamus


What are 3 important functions of the thalamus?

1. They channel the projections of sensory (pain, temperature, audition, and vision) information entering the lower levels of the nervous system to specific cortical areas.
2. They integrate sensorimotor information and project afferents from the basal ganglia, limbic system and cerebellum to the primary and premotor cortices
3. The thalamus and its circuit regulate functions of the associational cortex as well as cortically mediated cognitive functions


What nuclei are part of the Medial Nuclear Complex?

• Dorsomedial nucleus (DM)
• Midline nuclear complex


What nuclei are part of the Lateral Nuclear Complex?

• Lateral dorsal nucleus (LD)
• Lateral posterior nucleus (LP)


What nuclei are part of the Ventral Nuclear Complex?

• Ventral anterior nucleus (VA)
• Ventrolateral nucleus (VL)
• Ventral posterior nucleus (lateral and medial)
• Lateral geniculate body (LGB)
• Medial geniculate body (MGB)


Medial Nuclear Complex: Dorsomedial Nucleus

What passes through this nucleus?
What are its functions?
What would be the result of a lesion?

- Mammillothalamic tract, with connections to the structures associated with memory and learning, passes beneath
- Reverberating network of this nucleus is involved with the development of emotion, judgment and reasoning, memory language and cognitive functions
Lesion: Involvement of the underlying fibres of mammillothalamic tract


Medial Nuclear Complex: Midline Nuclear Complex

Where does it send projections?
What are its functions?

- With afferent from amygdaloid complex and reticular information and projections to amygdaloid nucleus and hypothalamus, clinically
- Known to serve important visceral and emotional functions


Lateral Nuclear Complex: Lateral Dorsal Nucleus

What are its functions?

- Also receives afferents from pretectal region in midbrain
- Contributes to visceral-sensory integration needed for any behavioural responses


Lateral Nuclear Complex: Lateral Posterior Nucleus

What are its functions?

- Reciprocal connections to superior parietal lobule, is likely involved with the information integration involving multiple modalities including vision, tactile, and audition


Lateral Nuclear Complex: Pulvinar Nucleus

What are its functions?
Where do its projections go?
What is it associated with?

- Considered to have a role in higher mental functions, with afferents from primary and associational visual cortices, and from visual-motor integrating area of superior colliculus, and with projections to the inferior association cortex of the parietal lobule with angular and supramarginal gyri
- Has been associated with regulation of mental functions, including language formation, lexical storage and processing, reading, and writing


Ventral Nuclear Complex: Ventral Anterior Nucleus

Where does it have afferents from? Where does it have projections to?
What are its functions?

- Has afferents from globus pallidus of basal ganglia and substantia nigra
- Projections to the premotor cortex
- Has role in execution and planning of skilled and sequential movements


Ventral Nuclear Complex: Ventrolateral Nucleus

What are its functions?
Where are afferents from?
What happens with disruption of circuitry?

-Important for regulation of volitional movements
- Important in coordinating different aspects of motor functions in coordinating different aspects of motor functions because it integrates input from basal ganglia with feedback from cerebellum before projecting the integrated info to primary motor cortex
- Afferents from contralateral cerebellar hemisphere and efferents to primary motor cortex underlie the nucleus's role in regulating cortically generated movements
- Disruption of circuitry results in abnormal movements.


Ventral Nuclear Complex: Ventral Posterior Nucleus

What does it do?

Serves as a thalamic relay center for somatosensation (pain, temperature, discriminative touch) from the body and face


Ventral Nuclear Complex: Ventral Posterior Lateral Nucleus

What does it do?
Where does it have afferents/efferents?

- Relays information related to somatic (pain, touch and temperature) sensation from the body; is uniquely situated to modulate somatic sensation
- Afferents from the body via the ventral and lateral spinothalamic tracts and medial lemniscus
- Efferent to the dorsal two-thirds of primary somesthetic cortex in postcentral gyrus


Ventral Nuclear Complex: Ventral Posterior Medial Nucleus

What does it do?
Where are its afferents?
Where do its projection fibres travel?

- Afferents from secondary fibres of trigeminal (CN V) nerve and efferents to the lower third of the primary somesthetic cortex, VPM is important in facial sensation
- Projection fibres from ventral nuclear complex travel through internal capsule and extend to primary somesthetic cortex in parietal lobe


Ventral Nuclear Complex: Lateral Geniculate Body

What does it do?
Where are its afferents?
What happens with pathology to the nucleus or its projections?

- Thalamic relay centre for the sensation of vision
- Afferents from the ipsilateral halves of both retinas/eyes and efferents to the primary visual cortex, mediates in transmission and integration of the visual information.
- Pathology: results in the loss of vision in contralateral halves of the visual fields = homonymous hemianopsia


Ventral Nuclear Complex: Medial Geniculate Body

What does it do?
Where are its afferents?
What is the result of pathology

- Primary relay centre for auditory information
-Afferent fibers from organ of Corti in both ears via fibers of lateral lemniscus and brachium of inferior colliculus, it projects to primary auditory cortex
- Fibers leaving nucleus constitute auditory radiations (geniculo-Heschl fibers) traveling through the internal capsule before terminating in the primary auditory cortex on the superior surface of the lateral fissure, the transverse gyri of Heschl
- Pathology: affect verbal processing and the ability to discriminate speech sounds in addition to a minimum attenuation of hearing sensitivity in both ears


Which nucleus? :

Is functionally related to the limbic brain (hippocampus, cingulate gyrus, and hypothalamus) and, in part, contributes to digestive, respiratory urogenital, emotional and endocrine functions. Regulate the hypothalamic and limbic influence on the neocortex

Anterior Nucleus


Which nucleus? :

Regulates thalamic neuronal activity participation, which influences cortical functions by inhibiting or facilitating the talamocortical relay

Reticular Nucleus


Which nucleus? :

As a whole, the system influences the excitability of the association cortex with both its projections and striatal collaterals to the cortex.
Is in a prime position to modulate the excitability and overall function of both the cortex and basal ganglia related to cognitive and sensorimotor function
- Complex consists of several nuclei interspersed in the core of the internal medullary lamina. Centromedian and parafasiculuar nucleus indirectly contribute to the diffuse reticular-brain activation system

Intralaminar nuclei


What is the role of the subthalamus?

- Connected to the globus pallidus via bidirectional fibers and it makes substantial contributions to motor functions.


Which structure contains all of these bodies: optic chiasm, mammillary bodies hypophysis (pituitary gland), infundibular stem (pituitary stalk) and tuber cinereum.?



What happens when there is hemorrhage in the dominant thalamus?

Shows persisting aphasic symptoms such as anomia


What is thalamic syndrome?

Disorder of somatosensory functions. It is characterized by increased or decreased thresholds for the sensations of touch, pain, and temperature on the contralateral half of the body